This invention relates generally to lamps that emit polarized light for example for use with reflective spatial light modulators.
Spatial light modulators may use a liquid crystal light valve to modulate light for display or projection of images. Such modulators may use reflective or transmissive technologies. Spatial light modulators may be formed on integrated circuits together with logic circuitry. Thus, integrated displays with integrated drive electronics may be formed.
As a result, spatial light modulators may be formed in a relatively cost effective fashion. Ultimately, such displays may be competitive with conventional displays such as cathode ray tubes. Generally, spatial light modulators utilize circularly polarized light which is reflected from a liquid crystal surface. That surface has its reflective properties modulated by underlying electrodes. The resulting displays may be able to modulate large light powers, without excessive heating, with reduced box sizes for the same screen size as compared to cathode ray tubes.
Reflective spatial light modulators need a bright source of circularly polarized light. Conventionally, a high pressure discharge source, such as a weakly ionized plasma, produce unpolarized light. The unpolarized light is then filtered through a circular polarizer. The polarizer transmits the circularly polarized photons and rejects photons of the opposite polarization state.
Ultimately some of the light from the light source passes outwardly for reflection from the spatial light modulator. The remaining light is trapped and absorbed inside the light source as wasted heat. Ideally, fifty percent of the amplitude of the initial light produced by the lamp can be emitted by the lamp cavity to the outside optics in the appropriate circularly polarized state. The other half of the light produced by the lamp is wasted. Thus, the light source must generate twice the amplitude that is actually used. This may result in unnecessary heating, unnecessary expense, and increased component size.
Thus, there is a need for better ways to produce a circularly polarized light source, for example in use in connection with reflective spatial light modulators.